HALLIWELL, N.A., HOCKNELL, A. and ROTHBERG, S., 1997. On the measurement of angular vibration displacements: a laser tiltmeter. Journal of Sound and Vibration, 208 (3), pp. 497 - 500.
A novel modification and use of the optical geometry which is used as the basis for the
Laser Torsional Vibrometer  is described. This latter instrument measures the torsional
oscillation (or local rotational speed fluctuation) of a rotating component of arbitrary
shape and in the presence of solid body vibrations of the component itself. The Laser
Torsional Vibrometer relies on the mean speed of rotation of the component to produce
a time resolved voltage analogue of the angular velocity. There are many cases of
engineering interest however where a component undergoes an angular oscillation about
an axis rather than a simple translation or rotation with a unidirectional angular velocity
In modal analysis for example where rotational and translation motions are of equal
importance the absence of suitable transducers means rotational mobilities are rarely
measured . In what follows it is shown how a modification to the optical geometry of
the Laser Torsional Vibrometer can produce an instrument which is capable of measuring
the local angular or tilt velocity in this situation and will therefore solve this problem.